Damper regulating system for fuel burning apparatus



G. F. GEIS 2,234,840

DAMPER REGULATING SYSTEM FOR FUEL BURNING APPARATUS March 11, 19-41.

Filed July 5, 1938 5 Sheets-Sheet l lNVENTOR 5601:961 Ge is Mmlh H, (3. IF. GEES 34,340

DAMPER REGULATING SYSTEM FOR FUEL BURNING APPARATUS Filed July 5, 1938 3 Sheets-Sheet 2 INVENTOR Mmfll 11,. 1141., F @515 24,40

DAMPER BEGULATING SYSTEM FOR FUEL BURNING APPARATUS Filed July 5, 19158 3 Sheets-Sheet 5 INVENTOR 6801:5761? Geis Patented Mar. 11, 1941 PATENT OFFICE DAMPER REGULATING SYSTEM FOR FUEL BURNING APPARATUS George F. Geis, ,John stown, William G. Hefner and C.

trustees Pa., assignor to Lawrence Evans,

Application July 5, 1938, Serial No. 217,357

Claims.

This invention relates to a fuel burning apparatus and particularly to a regulated draft system for such apparatus. The invention is particularly intended for use with the burning of solid fuel.

In the accompanying specification and drawings, the invention will be described particularly in connection with steam or hot water heating plants, but the invention is also applicable to other fuel burning equipment, including hot air furnaces used for heating plants.

Boilers and other heating plants used for the burning of solid fuel are usually provided with a door located at the base of the fuel burner known as a draft door. Another door is generally provided in the smoke hood or in h p p leading from the furnace to the flue which is called a check draft door. The purpose of the draft door is to control the admission of air for combustion purposes to the furnace. The purpose of the check draft is to control the draft to which the furnace is subjected. When heat is required the draft door is opened and the check draft door is closed. When a desired degree of temperature has been reached in the building in which the heating plant is installed, the check draft is opened and the draft is closed. Operation of these two doors controls the burning of the fuel and the amount of heat supplied to the build- It has heretofore been common practice to provide boilers with automatic regulating devices for operating the draft and check draft doors. Such devices have commonly comprised a long lever pivotally supported on top of the boiler. One end. of the lever is connected through a chain to one of the draft doors and the opposite end of the lever is connected by a chain to the other draft door. A pressure responsive device in the boiler is provided for moving the lever in one direction while a counterweight on the lever is provided to resist motion of the lever. Chains connecting the lever with the respective draft doors are usually provided with sufficient slack so that one door may remain closed while another one is being opened. These devices are not generally satisfactory, particularly in hot water heating plants and in domestic steam heating plants where there is never any wide variation in the steam pressure. These regulators as heretofore designed have not been sufficiently sensitive to respond to slight changes in boiler temperature and they have, moreover, had certain points in their operating ranges where they could respond only to a very considerable change in temperature in the boiler. This was due, for example, to the fact that under some conditions the load on opposite ends of the lever changes but the opening or closing of the door destroys 5 any balance between the loading on the two ends of the lever and imposes a non-uniform resistance to the heat responsive element that operates the lever. These controls have, therefore, not been generally satisfactory and attempts have been made to overcome the difficulty by using 10 much more elaborate and expensive types of controls as, for example, motor driven controls.

According to the present invention, I provide a damper control system which is highly sensitive throughout the complete operating range of the draft door and which can be set to operate within closely controlled limits. The invention is relatively simple and cheap to install. In overcoming the difficulty inherent in devices of this character as heretofore provided, the general construction and arrangement of the dampers is the same as that heretofore provided. How,- ever, heretofore both the draft door and the check draft door have been arranged to close 2 under the influence of gravity and to open under the operation of the automatic damper regulator. According to the present invention one of the doors is biased by gravity or otherwise to move to a normally open position and the other door is biased to move by gravity or otherwise to a normally closed position. By reason of this change, a normally constant load can be maintained on the operating lever throughout substantially the entire range of its movement. The invention further contemplates biasing the operatin'g lever for the damper control through adjustable means and to maintain the biasing force substantially constant throughout the range of movement of the lever. A third feature of the present invention, but one which is dispensed with 40 in certain modifications as will hereinafter be more fully described, is the transmission of mo tion from the operating lever of the damper controller to the door through an equalizing device by 'means of which the doors may be operated in the conventional sequence followed in hand firing, where one door is closed or nearly closed before the other is opened notwithstanding that the reverse biasing of the doors is contrary to the conventional arrangement.

The invention may be readily understood by reference to the accompanying drawings, in which Fig. 1 illustrates a side view of a boiler having a damper controlled system constructed in accordance with the present preferred embodiment of my invention;

Fig. 2 is a view similar to Fig. 1 in which both doors are shown in their closed position, this View representing the rear end of the furnace only and showing the doors arranged in a slightly different way;

Fig. 3 is a detail View of part of the biasing adjustment and inductor, this being on a larger scale than Fig. 1;

Fig. 4 is a detail view showing on a larger scale another part of the arrangement for biasing the load on the heat responsive actuating device;

Fig. 5 is a schematic view showing the manner in which the moment arm through which the biasing spring acts decreases as the tension on the biasing spring increases;

Fig. 6 is a view similar to Fig. 2 showing a slightly modified form of equalizer for transmitting motion from the rocking lever to the doors;

Fig. 7 is a side elevation of a modified form of actuating device;

Fig. 8 is a perspective view of the modified form of door actuating device shown in Fig. 7;

Fig. 9 is a view similar to Fig. 1 but on a smaller scale showing a slightly modified arrangement for operating the doors, the biasing mechanism, however, not being illustrated;

Fig. 10 is an end view of the apparatus shown in Fig. 9; and

Fig. 11 is a view similar to Fig. 9 of a further modification.

Referring first to Fig. 1 of the drawings, 2 designates a boiler supported on a base 3, the boiler and its base being more or less diagrammatically illustrated and being of any known or preferred construction. The front of the boiler is shown as being provided with a front plate 4 forming a part of the cover and having a rounded top shell 5. The remainder of the customary enclosing casing for the boiler is not shown but the boiler may be enclosed in any preferred way as is customary in the art, a sheet-metal shell usually being preferred for this purpose.

Set into the rear of the boiler is an actuator 6 responsive to heat generated in the fuel-burnlng apparatus. This device may be directly responsive to temperature within the boiler or may .be indirectly responsive to such temperature through the medium of the steam pressure. I prefer to use a device which is directly responsive to temperature rather than one which responds to steam pressure. Devices of this character are now well known to those skilled in the art and such devices have a rod 1 which is moved up with an increase in temperature and which can move down with a decrease in temperature. On the top of the member 6 are spaced lugs 8 having substantially triangular openings therein providing bearings for knife-edge trunnions 9 on an actuating lever I0, which lever passes between the lugs 8 and which is notched at ltla and engaged with by knife-edge at the top of the rod 7. The lever I6 has an abutment Illb which contacts with the top of the member 6 to limit the arcuate movement of the lever It in one direction. The lever I0 is provided also with an upstanding arm Hie, which is provided with an opening or slot through which one end of a rod H is passed. The rod H is provided with an adjustable knife-edge abutment !2 which bears against the rear face of the arm Mic. A wing nut 13, threaded onto the outer end of the rod l serves to adjust the fulcrum 0r abutment member I 2. This wing nut adjustment is particularly useful where it is usually positioned.

to set the minimum tension of the spring I 4 when the apparatus is first assembled. The forward end of the rod l i is connected to a tension spring M and the other end of the tension spring It connects to 9. lug l5 on an adjustable nut I 6, which rests on the top of the boiler and which is adapted to be concealed within the boiler casing. The nut i 6 has a threaded engagement with a bolt H, the bolt IT passing through the front casing or panel of the boiler and having a knob l'ia by means of which the bolt I! can be turned to move the nut forwardly or rearwardiy to change the tension on the spring i4. Supported on the underside of the curved portion 5 of the top of the front panel by means of lugs I3 is a sector-shaped indicator is visible through a window 29 in the panel portion 5. This indicator has a sector-like extension 634; with teeth thereon which engage in notches or teeth lfia on the nut H5. The arrangement is such that by turning the hand wheel ll'a the nut 16 can be moved forwardly or rearwardiy to adjust the tension on the spring Hi and this adjustment of the nut IE will move the indicator E9,

The purpose of the spring Hi, the connecting rod H and the adjustable nut I8 is to provide an adjustable resistance or load for the rod 1 of the thermal responsive actuating device 6 to operate against. If the tension exerted by the spring i4 is light, the member 7 will encounter little resistance or biasing force, and the heat responsive device will, therefore, begin to operate at relatively low temperatures. As the biasing force is increased by increasing the tension on the spring M, increased temperatures will have to be reached within the boiler before the memher i can overcome the load of the spring to operate the lever ID.

The lever iii is the actuating device for moving the draft and check draft doors. In the arrangement illustrated in Figs. 1 and 2, the lever it has a link 21 hung from its outer end and pivotally suspended from this link is a rocking beam 22. One end of the beam is connected through a flexible chain 23 to the check draft door 24 in the smoke hood of the boiler and the other end of the rocking beam is connected through chain 25 to the draft door 26 on the base 3 of the boiler. As shown in Figs. 1 and 2, the door 24 is pivoted at its bottom and is disposed at such an angle at the side of the smoke hood that it tends to swing open by gravity. The door 26, however, is hinged at its upper edge so that gravity tends to urge it to its closed position. In Fig. 1 the door 24 is shown in its fully closed position and the draft door 26 is in its fully open position. Fig. 2 is intended to be the same as Fig. 1, but for the purpose of more clearly showing or illustrating the manner in which the door 24 is biased to open by gravity, the door M is shown as being at the end of the smoke hood instead of at the side Consequently, corresponding reference numerals have been used in all cases on Figs. 1 and 2. In Fig. 2, the check raft door 24 is shown closed and the draft door 26 is also closed.

The link El on. the end of the lever l0 and the rocking beam 22 and the connecting chain 23 and 25 provide what may be termed an equalizer for transmitting motion from the lever [0 to the damper doors 2 and 28. With the draft door open, as shown in Fig. 1, and the check draft 24 closed, air is supplied to the fuel in the furnace under the boiler at the maximum rate and under the maximum draft to cause the fire to burn at the maximum rate. When the fluid in the boiler reaches a predetermined temperature, according to the tension which is on the spring 14, the rod 1 will begin to move up to rock the lever III, the

outer end of the lever l0 moving downwardly lowering the rocking beam 22 as a whole. If the doors Z4 and 2B are substantially balanced, as they should be, the moment exerted by the door 26 plus the long length of chain 25 exceeds the moment exerted by the door 24 and the short chain 23, and as the rocking beam 22 lowers the door 25 will close. When the door 26 has swung down to a nearly closed position, the adjustment is such that the door 24 will start to open and as the door 26 moves completely shut the check draft door 24 will continue to open as the outer or rearward end of the lever Iii continues to move down. When. the door 26 closes and the check draft 24 opens the draft in the boiler and the supply of air is diminished and the rate of combustion decreases. The apparatus will function to control the fire within very close ranges and this in turn is easily regulated by turning the hand wheel Ila on the front panel of the boiler and observingthe adjustment of the damper control by the indicator I9.

Themechanism is sensitive to extremely small variations in. the boiler temperature for three reasons. By reason of the fact that one door 24 is biased to normally move to an open position and the other door 26 is biased to normally move to a closed position, the two doors act in opposition to each other. The load exerted by the draft doors on the lever I0 is always substantially constant. This is more especially true where a rocking beam or other equalizer is used. The chains 23 and 25 are always under tension and the total load transmitted through the link it to the outer end of the lever I0 is substantially constant. By having the doors work against each other, the lever lfl has only to move to change the conditions of balance between them and operates, therefore, for practical purposes against a substantially uniform load. The opposed biasing of the doors plus the use of the equalizer are two of the three factors which make the equipment responsive to slight temperature changes and enable the fire to be controlled within close limits. A third factor is the arrangement of the biasing load as, for example, that exerted by the tension spring M in such manner as to at all times impose a substantially constant resistance to the movement of the lever under the influence of the rod 1. As a tension spring is stretched, it tends to exert an increased tension. In the present arrangement compensation is made for this increase in tension by changing the moment arm through which the spring operates to oppose movement of the lever Hi. This may be readily understood by reference to Fig. 5 in which I have diagrammatically shown the manner in which the spring exerts its tension through a decreasing moment arm as the spring is stretched. This is explained by the fact that the arm we on the lever III is so positioned with respect to the point about which the lever 10 pivots that as the lever Ill rocks under the influence of the member I to lower the outer end of the lever the point of connection between the rod H and the projection We moves progressively closer into line with the center so that as the spring is stretched it exerts its force through a the operating element 7. In the diagramin Fig. 5, a designates the lever I0, b is the pivot about which the lever Hi fulcrums and c is the point of connection between the connecting rod and spring (1 and the lever a. The member 1 is indicated in thisdiagram as e. As 2 exert an upward force on one end of lever a point 0 moves progressively to the positions c and 0'', thus moving progressively closer into line with the center I). By properly designing the relation of the points I) and c the decrease in the moment arm through which the spring i effective can compensate for the increase in the tension excited by the spring as it is stretched.

The arrangement shown in Fig. 6 is essentially the same as that heretofore described and similar reference numerals have been used to indicate corresponding parts. However, instead of there being a rocking beam suspended from the outer end of the lever I0 a link 30 is suspended from the lever and a pulley 3| is pivotally supported by this link. A continuous chain 32 connects the check draft door 24 and the draft door 26. This pulley arrangement provides an equalizing device which is generally equivalent to the rocking beam 22.

Figs. 7 and 8 illustrate a further modification, wherein the thermally responsive operating device transmits rotary movement to an operating member instead of a lever such 'as the lever It! In these figures the thermally responsive operating device is designated generally as 35 and 36 is the vertically movable rod which it operates. Supported in bearings 3'! on the member 35 is a shaft 38 having an oifset lug 39 which engages the terminal of the rod 36. The outer end of the shaft 38 is provided with an offset crank 48 from which is hung a link 4! carrying a rocking beam or other equalizer 42. Chains 43 and 44 are suspended from the opposite ends of this rocking beam. In operation the member 35 pushing up against the lug 39 rotates the shaft 33, swinging the crank 40 through an arc to move the rocking beam 42. A torsion spring 45 has one end attached to the shaft 38. The other end of the torsion spring 45 is attached to an adjusting rod 45. The rod 46 passes through the front panel 41 of the boiler and is provided with an operating crank 48. The crank 48 may have a detent at 48a adapted to enter any one of several holes in the front pan-e1 41 of the boiler. By pulling out on the crank 43 to a slight extent and turning it the torsion of the spring 45 can be increased or diminished to vary the biasing force which the actuating device 35 must overcome to rotate the shaft 38. The torsion spring 45, like the tension spring M of Fig. l,

has the property that as it is wound tighter it exerts an increase in force. To compensate for this some arrangement such as that i1lustrated in Fig. 5 should be employed. For example, in Fig. 7 I have shown shaft 38 as being provided with a radially extending arm 49 on which is a counterweight 50. As the shaft 38 rotates in a clockwise direction, the counterweight provided for compensating for the increase in the force exerted by the spring 45 as the shaft 38 rotates under the influence of the actuating device 35 with its movable member 3'5.

While it is desirable to provide an equalizer as illustrated, for instance in Figs. 1 and 6, it is not necessary that such an equalizer be employed. Fig. 9 illustrates an embodiment of my invention where such an equalizer is not used. In this figure 5| designates the boiler and 52 is the actuating device and 53 is a lever corresponding to the lever H] of Fig. l. The biasing mechanism for resisting movement of the lever 53 is not illustrated, but it will be understood that a mechanism such as the rod H and spring M of Fig. 1 may be employed with the lever 53. A flexible connector such as a chain 54 has its upper end attached to one end of the lever 53 and its lower end attached to the check draft door 55, the check draft door 55 being biased to open under the influence of gravity. From the check draft door a chain 56 extends to the draft door 51, the draft door 51 being biased to close under the influence of gravity. With this arrangement the check draft door 55 tends to open as the door 5'! closes and vice versa. Thus, the load on the end of the lever arm 53 is always constant unless the lever arm moves past a point where the draft door 51 is fully closed.

The arrangement shown in Fig. 11 is generally similar to that seen in Figs. 9 and 10 and corresponding numerals have been used to indicate corresponding parts. In place of there being a substantially continuous chain to which. both doors are attached, this modification shows one chain 58 extending between the lever 53 and the check draft door 55, and an entirely separate chain 59 extending between the lever 53 and the draft door 57.

The foregoing modifications are illustrative of certain embodiments of my invention, and it will be apparent to those skilled in the art that various changes and modifications may be made in the specific construction and arrangement of parts to effect the same results.

The principal advantage of the invention resides in the provision of a damper control of relatively simple construction which is extremely sensitive and. which can be adjusted to operate within a given temperature range. It is quite desirable to have a mechanism which is sensitive throughout its operating range, and this is especially true where a steam boiler is provided with a hot water heating coil for furnishing a source of hot water supply. In such installations it is frequently desirable to fire the boiler to heat hot water but not to heat the building. Where a steam boiler is used, the fire should be regulated to a point where Water in the boiler will adequately heat the water heating coil but below the point where steam will be generated. In cold weather, of course, the regulator is changed so that the building may be heated. The present invention in providing an indicator for the regulator enables the damper mechanism to be set for any particular condition of operation. The invention has particular advantages where a rocking beam or other equalizing device is used in that it is possible to so adjust the device that one door will just begin to open a little before the other one has closed so that there may be times when two doors are in operation and other times when only one door is in operation, but the load on the actuating lever will be the same in all cases. The invention permits both the draft door and the check draft door to be at the same end or side of the furnace or boiler and eliminates any complicated system of pulleys or chains and it eliminates any requirement for chains passing down the front of the furnace or boiler.

Other advantages are also secured by the invention.

The actuating device for moving the damper operating lever up and down is, as previously indicated, of any well-known or desired construction, but I prefer to use one which is directly responsive to temperature changes rather than one which is responsive to steam pressure in the boiler, although either a device responding to a change of temperature or a device responding to a change of pressure induced by a change of temperature is contemplated under the term heat responsive actuating device. The former will serve better where the boiler is being operated in warm weather to provide a hot water supply without any substantial steam pressure being generated.

While I have shown and described certain specific embodiments of my invention it will be understood that these are merely illustrative of my invention and that the invention may be otherwise embodied within the scope of the following claims.

I claim:

1. Fuel burning apparatus having draft and check draft doors, one of which is biased to move to a closed position and the other of which is biased to move to an open position, an operating lever, an actuator responsive to heat generated in the fuel burning apparatus for operating the lever, an equalizer connected with the lever to be raised or lowered thereby, and a flexible operating connection between one door and one side of the equalizer, and a fiexible operating connection between the other door and the other side of the equalizer.

2. Fuel burning apparatus having draft and check draft doors, one of the doors being biased to move to a closed position and the other of ,said doors being biased to move to an open position, an actuator responsive to heat generated by the fuel burning apparatus for operating both doors, a lever operated by the actuator, a rocking beam pivotally suspended from the lever and flexible connections extending from the opposite ends of the rocking beam to the respective doors.

3. A combustion control mechanism for fuel burning apparatus comprising an actuator responsive to heat generated in the fuel burning apparatus, a lever with which the actuator cooperates, check draft and draft doors oppositely biased so that one tends to move to an open position and the other tends to move toward a closed position, an equalizer element suspended from one end of the lever, operating connections extending from the opposite sides of the equalizer element to the doors, means for biasing the lever against movement by the actuator and comprising a spring, means for adjusting the force exerted by the spring, and means whereby as the lever moves against the action of the spring and thus increases the force which the spring exerts at least some of the biasing force will be exerted against the lever through a decreasing moment arm and thereby compensate for the increase in force exerted by the spring when the lever moves against the biasing spring.

4. A combustion control mechanism for fuel burning apparatus comprising an actuator responsive to heat generated in the fuel burning apparatus, a lever operated in one direction by the actuator, biasing means for resisting movement of the lever by the actuator and for moving the lever in the opposite direction, draft and check draft doors oppositely biased so that one tends to normally open and the other to normally close, flexible connections for transmit ting motion from the lever to the doors, said lever having an offset extension thereon, the biasing means comprising a tension spring having one end attached to said extension and the other end attached to an adjusting element, means for moving the adjusting element to vary the tension exerted by the spring, the offset extension on the lever being such that as the lever is moved by the actuator against the tension of the spring to stretch the spring the moment arm through which the tension of the spring is exerted decreases,

5. A combustion control mechanism for fuel burning apparatus comprising an actuator responsive to heat generated in the fuel burning apparatus, a lever operated in one direction by the actuator, biasing means for resisting movement of the lever by the actuator and for moving the lever in the opposite direction, draft and check draft doors oppositely biased so that one tends to normally open and the other to normally close, flexible connections for transmitting motion from one end of the lever to both of the doors, said lever having an offset extension thereon, the biasing means comprising a tension spring having one end attached to said extension and the other end attached to an adjusting element, means for moving the adjusting element to vary the tension exerted by the spring, the offset extension on the lever being such that as the lever is moved by the actuator against the tension of the spring to stretch the spring the moment arm through which the tension of the spring is exerted decreases, and an indicator operated by said adjusting means.

6. A combustion control mechanism for fuel burning apparatus comprising an actuator responsive to heat generated in the fuel burning apparatus, a lever operated thereby, check draft and draft doors normally biased so that one tends to normally open and the other to normally close, an equalizer suspended from one end of the lever, a connection from one door to one side of the equalizer, and a connection from the other door to the other side of the equalizer, biasing means for the lever against which the actuator works, the lever having an offset extension thereon, the biasing means comprising a spring having one end connected with the extension and the opposite end anchored and adjusting means for varying the tension of the spring independently of the position of the lever.

'7. Fuel-burning apparatus having draft and check draft doors which are supported to swing for counter-acting such movement of the lever,

and temperature-responsive actuating means for operating the lever.

8. Fuel-burning apparatus having draft and check draft doors which are supported to swing from open to closed position, the check draft door being biased normally to swing to an open posi tion and the draft door being biased normally to swing to a closed position, an operating lever, pivotally supported means hung from the operating lever through which the two doors are operatively connected to each other, there being flexible connections from each door to said pivotally supported means, said doors thus serving to urge the lever to move in one direction, yielding means for counteracting such movement of the lever, and actuating means responsive to heat generated in the fuel-burning apparatus for operating the lever against the force of the counteracting means.

9. Fuel burning apparatus having draft and check draft doors, one of which is biased to move to a closed position and the other of which is biased to move to an open position, an operating lever, an actuator responsive to heat generated in the fuel burning apparatus for operating the lever, an equalizer connected with the lever to be raised or lowered thereby, and an operating connection between one door and one side of the equalizer, and an operating connection between the other door and the other side of the equalizer.

10. Fuel-burning apparatus having draft and check draft doors which are supported to swing from open to closed position, one of the doors being biased to normally swing to an open position and the other being biased to normally swing to a closed position, an operating lever, pivotally supported means hung from the operating lever through which the two doors are operatively connected with each other, there being connections from each door to said pivotally supported means, said doors thus serving to urge the lever to move in one direction, means for counteracting such movement of the lever, and temperature-responsive actuating means for operating the lever.

GEORGE F. GEIS. 

